Add Pramfs filesystem to the kernel mainline

Description

Many embedded systems have a block of non-volatile RAM seperate from
normal system memory, i.e. of which the kernel maintains no memory page
descriptors. For such systems it would be beneficial to mount a
read/write filesystem over this "I/O memory", for storing frequently
accessed data that must survive system reboots and power cycles. An
example usage might be system logs under /var/log, or a user address
book in a cell phone or PDA.

Currently Linux has no support for a persistent, non-volatile RAM-based
filesystem, persistent meaning the filesystem survives a system reboot
or power cycle intact. The existing RAM-based filesystems such as tmpfs
and ramfs have no actual backing store but exist entirely in the page
and buffer caches, hence the filesystem disappears after a system reboot
or power cycle.

In the last review (end of June) some people have asked some
modifications. The bigger ones are: fs layout endianess indipendent and
a protection against system crash (a little journaling system for
example). In the last version I closed all the open issues with the
exception of the last one. It would be nice to close even this point to
be ready for the mainline!

Comments

Tim Bird writes:

Pramfs has been hanging around outside of mainline
since CELF was created (2003), and was on our list of stuff
to try to mainline then. It's been attempted at least 3 times,
but maybe with your fixups to address feedback from LKML it
can finally make it in.
I have my doubts as to how important the journaling feature is.